package com.ninja.sqlSession;

import com.ninja.config.BoundSql;
import com.ninja.pojo.config.Configuration;
import com.ninja.pojo.config.MappedStatement;
import com.ninja.utils.GenericTokenParser;
import com.ninja.utils.ParameterMapping;
import com.ninja.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor {
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        PreparedStatement preparedStatement = toPrepareForExecute(configuration,mappedStatement,params);
        //执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();

        //封装返回结果集
        while (resultSet.next()){
            Object o =resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {

                // 字段名
                String columnName = metaData.getColumnName(i);
                // 字段的值
                Object value = resultSet.getObject(columnName);

                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }

    @Override
    public int notQuery(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        PreparedStatement preparedStatement = toPrepareForExecute(configuration,mappedStatement,params);
        //执行sql,并返回影响的行数
        return preparedStatement.executeUpdate();
    }


    public PreparedStatement toPrepareForExecute(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception{
        //1. 注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        //2. 获取sql语句,并转换成jdbc可以执行的格式
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);
        //3. 获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4. 设置参数, 首先获取参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramtertypeClass = getClassType(paramterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            //getField 仅能获取类(及其父类可以自己测试) public属性成员
            //getDeclaredFiled 仅能获取类本身的属性成员（包括私有、共有、保护）
            Field declaredField = paramtertypeClass.getDeclaredField(content);
            //暴力访问，允许通过反射获取私有变量的值,在访问时会忽略访问修饰符的检查
            declaredField.setAccessible(true);
            //方法返回指定对象中该Field的值
            Object o = declaredField.get(params[0]);

            preparedStatement.setObject(i+1,o);
        }
        return preparedStatement;
    }


    /**
     * 完成对#{}的解析工作：1.将#{}使用?进行代替，2.解析出#{}里面的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);

        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql,parameterMappings);
        return boundSql;
    }

    //根据参数的全路径,获取参数的class对象
    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if(paramterType!=null){
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;
    }


}
